Mixer



' Aug. 19, 1941. R CAMP 2,253,059

MIXER Fi led Sept. 20, 1939 3 Sheets-Sheet l in I [N VEN TOR THO/VHS 1. CAMP ATTORNEZZ;

P M A G P MIXER Filed Sept. 20, 1959 3 Sheets-Sheet 2 11v VENTOR THO/W75 P! C/Y/ IP ATTORNEY Patented Aug. 19, 1941 mxna Thomas P. Camp, Arlington Heights, 111., asslgnor to United States Gypsum Company, Chicago, Ill., a corporation of Illinois Application September 20, 1939, Serial No. 295,757

4 Claims.

This invention relates to mixers, and mixing methods, and has reference more particularly to mixers and mixing methods for preparing slurries of cementitious materials, such as gypsum plaster and the like.

It has been customary to mix gypsum plaster by introducing calcined gypsum and water at approximately the center of rotation of a rapidly rotating disc. The axis of the disc is arranged vertically and the disc is enclosed in a housing having a discharge port. The mixed slurry is discharged from the port onto a moving strip of paper forming the bottom cover sheet of the finished board. Mixing pins are. provided on the upper surface of the disc and on the bottom surface of the housing cover to mix the water with the calcined gypsum to produce a slurry. It is customary in the manufacture of plaster boards, to pass three streams of paper under the mixer so as to produce three streams of board simultaneously. Considerable diiiiculty has been experienced in dividing the slurry discharge into three equal streams. In certain cases it has been found that the time interval of mixing was too short in order to thoroughly mix the water and calcined gypsum. The addition of a stable foam to the slurry as a density reducing agent, also requires special provisions in order to prevent the foam from breaking down.

An object of the invention therefore, is to provide a mixer and mixing method of the high speed centrifugal type in which the time of mixing may be increased at will to a predetermined extent.

Another object of the invention is to provide a centrifugal mixer in which a plurality of equal streams of slurry may be delivered simultaneously from the mixer housing.

A further object of the invention is to provide a mixer and mixing method in which a stable foam may be successfully mixed with the slurry without breaking down; also to improve mixers and mixing methods in other respects hereinafter specified and claimed.

Reference is to be had to the accompanying drawings forming a part of this specification, in which- Fig. l is a plan view of the mixer positioned adjacent a board machine,

Fig. 2 is a plan view on a large scale of a modifled form of mixer,

Fig. 3 is an elevation of discharge gates on the mixer shown in Fig. 2,

Fig. 4 is a sectional plan view of the mixer shown in Fig. 2,

Fig. 5 is a sectional elevation through the mixer taken on line 55 of Fig. 2,

Figs. 6 and 7 are fragmentary sectional elevations through the mixer taken on lines 6-6 and 1-1 of Fig. 4,

Fig. 8 is a sectional plan view through a further modified form of mixer, and

Fig. 9 is a sectional elevation through the mixer taken on line 6-6 of Fig. 8.

Referring to the drawings by numerals, the

mixer in its preferred form (Figs. 2-7) comprises a metal disc Ii which is secured at its center to a shaft l6 having a frusto-conical section I! near the top thereof. A collar it fits over the shaft section I! and is provided with an outstanding annular flange l9 upon which the disc I5 is supported. A clamping collar 20 is attached by key 2! to the upper end 22 of shaft l6, being held in place axially by a nut 23. The disc I6 is thus clamped between the collar 20 and flange i9. Downwardly extending lugs 24 formed on the collar 20 extend into slots in the disc i5 to firmly unite the various parts. A housing bottom 25 extends under the disc l5 and is secured to an annular peripheral ring 26 by bolts 21. A housing cover 26 is also secured to the ring 26 by the bolts 21.

A port opening 29 is formed in the cover 28 for continuously introducing calcined gypsum or stucco and its compositions, or other cementitious mixture, into the housing near the center of rotation of the disc I5. A plurality of water pipes 30 also pass through the cover 28, said water mixing continuously with the cementitious material to form a slurry. Pins 3| are secured to the cover it, the bottoms of said pins having a slight clearance above the upper surface of disc 15. Pins 32 are secured to the upper surface of disc is to cooperate with pins 3i in securing a thorough mixing of the slurry as it is thrown outwardly under the action of centrifugal force supplied by the disc it.

One of the salient features of my invention comprises an annular ring 34 which is secured by bolts 35 to the cover 28, said ring being interrupted to form an opening or port 36. The ring 34 is positioned at a substantial distance from the housing ring 26 and the port 36 is offset relative to a housing discharge port 3'! so that the slurry is caused by ring 34 to make an extra spiral passage around the housing outside of the ring 34 before discharging from the port 31. This added time interval of mixing caused by the ring 34 insures a much more complete mixing of the slurry before being discharged from the port 31. A pipe 38 leads through the cover 28 between rings 26 and 34 to introduce stable foam into the slurry a short time before discharge from the port 31. By introducing foam at this point, prolonged mixing of the foam is avoided so that the bubbles forming the foam are not broken down. Accelerator or retarder as desired may be introduced between rings 26 and 34 through pipe 39 which is connected to cover 26. A pipe 40 also leads through cover 26 to admit wash water to the mixer housing when finishing operation of the mixer.

The cover 25 is provided with a hinged lid 4| which gives access to the inside of the mixer for cleaning or repairs. Clamp bolts 42 hold the lid 4i down firmly when the mixer is in operation. Considerable care must be taken, in locating the mixing pins 32 to obtain the proper mixing action. In Fig. 6 the pins 32 are located close to the ring 34 and in Fig. '1 said pins are spaced substantially apart from the ring 34. The shaft I6 is supported in suitable bearings 43 and 44 secured to framework 45. The discharge port 31 is divided by partitions 45 and 46 into a plurality of spouts or outlets 41. 48 and 49. Gates 50, and 52 are-provided in the spouts 41, 48 and 49 respectively to control the flow of slurry from each spout. Levers 53, 54 and 55 control the opening of the gates 50, 5| and 52 respectively. Each of the spouts 41, 48! and 49 deliver slurry onto three moving strips of paper 56, 51 and 58 respectively. If desired pipes 59, 60 and 6| of varying lengths may lead from the spouts 41, 48 and 49 respectively as shown in Fig. 1 to obtain a better distribution of the slurry. If it is desired to obtain a still further increase in mixing time, the form of mixer shown in Figs. 8 and 9 may be used. In this mixer, an additional ring 63 may be attached to cover 28, said ring having an outlet port 64 offset from the port 36. The slurry will thus make two complete revolutions before passing through the discharge port 31. n I

The new mixer is a marked improvement over the old type mixer in that it has a higher mixing capacity for the same diameter and speed, and also in that it will produce a smooth mix, free from lumps of dry or partially mixed stucco, from a stucco which normally cannot be satisfactorily soaked in the old type mixer. A further advantage is that momentary variations in thequantity of stucco fed to this mixer are given an opportunity to even out with the result that the mix issuin from the soaker is more uniform than that produced by the old type mixer. A still further advantage of the new mixer is that its use with a slow setting stucco will result in a quicker final set than would otherwise be the case without the addition of any excess of accelerator. This last is due of course to the almost doubled agitation which the slurry receives.

A further advantage of this mixer would be particularly noticeable where several different additive agents are designed to be added at sheet and thereby reducing the quantities required for the same volume expansion. Other advantages such as the elimination of the ball type spindle mixer with its attendant expense should also be considered.

I would state in conclusion that while the illustrated examples constitute a practical embodiment of my invention, I do not wish to limit myself precisely to these details since manifestly the same may be considerably varied withport.

out departing from the spirit of the invention as defined in the appended claims.

Having thus described my invention, I claim as new and desire to secure by Letters Patent:

1. In a mixing device, a disc arranged to rotate about a vertical axis, means for continuously feeding cementitious material and water onto said disc near said axis, said disc normally rotating at a speed sufficient to quickly discharge said material therefrom by centrifugal force, a housing substantially surrounding said disc, said housing having a cover, mixing members on said cover and disc, and a stationary ring-like partition secured to said cover and substantially surrounding said axis, said housing and said ring having ports in ofl'set relation so as to cause the mixing slurry to follow a positive, substantially spiral path longer than its normal path to prolong the mixing period before discharging from said housing port without materially reducing the output.

2. In a mixing device, a disc arranged to rotate about a vertical axis, a housing substantially surrounding said disc, said housing having a cover and a peripheral discharge port, means for continuousl feeding cementitious material and water onto said disc near said axis, said disc having a normal speed of rotation suincient to quickly discharge the material therefrom by centrifugal force, mixing members on said cover and disc, and a stationary split ring partition inside said housing above said disc, said partition having a port in offset relation to said housing port so as to cause mixed slurry to follow a positive, substantially spiral path longer than its normal path to prolong the mixing period before passing to said housing 3. In a mixing device, a disc arranged to rotate about a vertical axis, a housing substantially surrounding said disc, said housing having a cover and a peripheral discharge port, means for continuously feeding cementitious material and water onto said disc near said axis, said disc having a normal speed of rotation sufilcient to quickly discharge said material therefrom by centrifugal force, mixing members on said cover and disc, and a plurality of stationary ring-like porting means to apply a sufiicient centrifugal force from adjacent an axis to slurry forming materials delivered to said machine to normally rapidly expel said material from said supporting means, and means to continuously mix said materials into slurry while in said machine, of a substantially concentric baflle in the normal radial path of movement of said slurry over said supporting means in response to said centrifugal force, said baflle being of sufficient extent to materially oppose said centrifugal force applied to said slurry and to materially retard the radial movement thereof and to materially elongate the path of said materials through said machine and increase the time of mixin without 

